At a Congressional briefing and at a separate news conference, the E.P.A. administrator, Stephen L. Johnson, described for the first time the wide variety of problems the agency was confronting, including the difficulty of determining the extent and toxicity of the sludge left by the floodwaters. Mr. Johnson said the agency was using aircraft to test for air pollution and taking daily samples of floodwaters and the sludge. The sampling is concentrated in residential areas.

The agency has not completed or released details about specific strategies and the scientific protocols it is using as it tries to analyze the hazards posed by what Mr. Johnson called "the largest national disaster that we at E.P.A., or we believe, that the nation has faced."

Mr. Johnson said early tests did not look for hazardous petrochemical byproducts like benzene because the presence of oil and gasoline was obvious.

In the wake of the Sept. 11 attacks in New York, the E.P.A. came under criticism by prominent members of New York's Congressional delegation for declaring the air near ground zero safe based largely on testing for asbestos. Later, the agency's inspector general criticized agency officials as making this declaration without sufficient scientific evidence.

In the past two days, Mayor Nagin and Mr. Johnson offered differing accounts of the federal agency's role in certifying the city's neighborhoods as fit for human occupancy.

Mr. Nagin said Tuesday that he was awaiting an E.P.A. report on air and water quality in four unflooded neighborhoods. On Wednesday, Col. Terry J. Ebbert, the head of homeland security for New Orleans, restated the remark. But public affairs officers at both the environmental agency and the Louisiana State Department of Environmental Quality said they knew of no such report.

Meanwhile, EPA Policy Analyst Hugh Kauffman, apparently hoping for a demotion and a transfer to the Marianas Islands, tells Morning Sedition (via Buzzflash) that the EPA has definite knowledge of chemical contamination that it is witholding from the public.

All of the oil and chemical companies that own storage tanks, facilities in that area that were flooded or impacted are required to publish with our regional office in Dallas instantly—whenever there’s a release; whenever there’s a breakage from pipelines, from storage tanks, refineries. The regional office, under orders, is not releasing that information to the public, and the Society of Environmental Journalists has sued EPA and the Federal Government to try and get that information released, so the public will see the full magnitude of how much toxic material they are being exposed to in that region of the country.

Interestingly, these assertions are not contradictory: EPA says it isn't bothering to test for hazardous petroleum byproducts such as aromatic hydrocarbons because they're obviously present. Meantime, people are working in the flood zone, and some are even living there, and they aren't being given any warning. Mr. Johnson doesn't deny that, he affirms it. Or am I missing something here?

Addendum:WWL TV in New Orleans has compiled what information it can about the extent of the environmental catastrophe. I note that much of the coverage I've seen in the past couple of days is happy talk about how the cleanup is progressing and people are starting to go home. I really don't think so.